Appreciate the desire to use a battery you have... Consider "D" cells. Variously reported as having 15-20Ah of capacity. You mentioned you might be able to use a 5V rail, so 4 in series. Two or three strings in parallel to be safe. -Denny On Mon, Oct 14, 2013 at 2:18 PM, Neil wrote: > Quick question on standard (NON deep-cycle) automotive lead-acid > batteries... what is lowest level that the Amp-Hour rating is > specified for? IE: For a group 34 battery with an ~50AH rating, does > it mean that drawing 1A for 50 hours will discharge it to it's > full-discharged (~10.5V) state? > > And here's the context... I need to power some displays for a trade > show. Expected power consumption is 900mA, but I'll use 1A to be a > bit conservative. The show has 32 operating hours (4 days), and with > some quick circuitry, I intend to start it automatically 1 hour before > and 1 hour after each day, so 40 hours total (plus the control > circuit, which I'll ignore for now as it's relatively negligible. So > I need 40Ah. If a standard 50Ah battery takes it to complete > discharge, I'm uncomfortable. If that's to some same level that will > not damage the battery, I'm fine. > > Cheers, > -Neil. > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .